The present invention refers to a device for treating a substantially gaseous medium, including a number of parallel plates which are connected to each other and provided adjacent to each other in such a manner that they by means of port holes of the plates form a first channel, which is arranged to transport the gaseous medium, and at least a second channel, which is separated from but in heat transferring contact with the first channel and which is arranged to transport a cooling medium for cooling the gaseous medium, wherein at least a part of the first channel forms a separation part and is arranged to separate liquid from the gaseous medium.
Such devices are used for dehumidifying of pressurised air from compressors before the pressurised air is supplied to pneumatic tools or machines, wherein the supplied pressurised air is first cooled by means of the heat exchanger part and thereafter moisture of the pressurised air is permitted to condense, whereafter the pressurised air and the condensate are separated in the separation part. It is known to design the heat exchanger part and the separation part as separate units, which has the disadvantage that a significant number of components and connection conduits are required. However, it has proved to be difficult to provide, at acceptable costs, a single unit for the heat exchanger part as well as the separation part due to the high pressures to be born by such a unit. In normal cases the parts are to bear a pressure of 8 bars, but there are also pneumatic systems operating at 13 bars and even higher pressures.
U.S. Pat. No. 5,727,623 discloses a device for drying pressurised air for pneumatic systems. The known device includes a heat exchanger part, having a number of parallel plates which are provided adjacent to each other in such a manner that they form a first channel and a second channel, which is separated from but in heat transferring contact with the first channel, and a separation part. The air to be dried is transported through the first channel of the heat exchanger part for cooling of the air and thereafter through the separation part for separating liquid from the air. The separation part is formed by a centrally provided chamber in which the pressurised air is permitted to condense. Although it is defined in this document that the separation part may include baffles to facilitate the condensing of the moisture present in the air, the supporting parts of the separation part appear to be formed by the circular cylindrical casing defining the chamber.
The object of the present invention is to provide an improved device for treating a gaseous medium, in particular for drying pressurised air.
This object is obtained by the device initially defined, which is characterised in that said separation part of the first channel is formed by a plurality of plate interspaces between one part of said plates, wherein at least one of the plates, delimiting one of said plate interspaces, is arranged to be passed by the gaseous medium on both sides thereof.
Thanks to the fact that the device is made of several parallel, adjacent plates, which are connected to each other, a very high strength of the device is obtained in an easy manner, which device thus may resist high inner pressures. By one or a plurality of plates, which on both sides are passed by the gaseous medium, large surfaces of the first channel are created, which in an efficient manner may increase the absorption of liquid, and in addition a relatively large total cross sectional area of the part of the first channel, which is intended to absorb liquid from the gaseous medium, is obtained. In such a manner, the flow velocity through this part of the first channel may be kept on a low level, which enables a high degree of separation. Furthermore, several distinct changes of direction for the gaseous medium are obtained by the plate arrangement of the separation part. Such changes of direction, which are substantially 90xc2x0, contribute to a more efficient separation of liquid than the one which may be obtained by a separation chamber of the type disclosed in U.S. Pat. No. 5,727,623.
According to an embodiment of the invention, the plates form a common plate package. In such a way it is possible to provide a very compact and pressure resistant unit of plates of the type which normally are used in plate heat exchangers. The plates are advantageously connected to each other by brazing. The different parts may be given the desired functions by pressing the area around the port holes of the plates in a suitable manner. Thereby, the plates, at least seen in a section extending substantially in parallel with the plates, may have substantially equal external dimensions.
According to a further embodiment of the invention, said separation part includes an outlet member for the discharge of the separated liquid. Advantageously, the plates are provided in such a manner that they extend substantially in parallel with a vertical plane, wherein the outlet member is provided in a lower part of said separation part. In such a way, the moisture which condenses will simply flow out of the separation part.
According to a further embodiment of the invention, the second channel includes a first channel portion, which is arranged to form a precooler for transporting a first cooling medium, and a second channel portion, which is arranged to form an evaporator for transporting a second cooling medium. In such a way, an efficient heat exchange is obtained, wherein the incoming gaseous medium is first precooled to a suitable temperature before it in the evaporator is subjected to a strong cooling by means of the second cooling medium which may re-circulate through said second channel portion. Advantageously, the evaporator is provided between the precooler and said separation part. In such a way, the gaseous medium will flow through the device from its one end to its second end and thereby successively pass through the port holes of successively located plates. Thereby, channels closed from said separation part may advantageously extend through said separation part and be arranged to enable the transportation of the second cooling medium to and from the evaporator. Alternatively, said separation part may be provided between the precooler and the evaporator. In such a way, the supply of the second cooling medium to the evaporator is facilitated.
According to a further embodiment of the invention, the first channel extends to an outlet of said separation part and is connected via an external or internal conduit to the second channel of the precooler, wherein the conduit is arranged to convey the gaseous medium from said outlet to the second channel of the precooler for heat exchange with the incoming gaseous medium. In such a way, the precooling of the gaseous medium mentioned above may be obtained in an easy and efficient manner. At the same time a heating of the gaseous medium is obtained by such a transportation of the gaseous medium before this leaves the device. Such a heating is desired in many pneumatic systems.
According to a further embodiment of the invention, at least a part of the second channel is formed by two of said plates, which are positioned adjacent to each other in such a manner that said part of the second channel extends therebetween, wherein said separation part of the first channel extends on both sides of said part of the second channel. Thereby, said part of the second channel may be included by the second channel portion. Furthermore, the plates, included by said separation part, may be arranged in such a way that each third interspace, which is formed between adjacent plates, forms a part of the second channel whereas the remaining interspaces, which are formed between adjacent plates, form a part of the first channel. Advantageously, at least one of said plate interspaces forming said separation part may include surface enlarging means.